Analysis of gas streams



Jan. 6, 1970 a. o. AYERS ANALYSIS OF GAS STREAMS Filed July 18. i966 .mOFUwPmO AU F Q l w R S E o R N T E R M M .Mm mm V Q T v mm wm mm mm w B. www A UW .QM

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I my fl.) mm u N NI u l@ m l United States Patent 3,488,155 ANALYSIS 0F GAS STREAMS Buell 0. Ayers, Bartlesville, Okla., assigner to Phillips Petroleum Company, a corporation of Delaware Filed July 18, 1966, Ser. No. 565,842 lut. Cl. Gtlln 33/04, 33/ 06 U.S. Cl. 23-232 13 Claims ABSTRACT OF THE DISCLOSURE A process and apparatus in which hydrogen is added to a gaseous hydrocarbon stream which may contain hydrogenatable material, and the amount of hydrogenatable material is indicated by the difference in temperature of said gas stream, measured rst before and second during or after hydrogenation over a hydrogenation catalyst. The components of said gaseous hydrocarbon stream of different molecular weight may tirst be spaced apart by the difr'erential rate of their passage through a gas chromatography column. By measuring the degree of hydrogenation, the composition of the stream can be controlled to contain a predetermined proportion of hydrogenatable material. By measuring the amount of hydrogen in the etuent from the hydrogenation zone, the composition of the stream can be controlled to contain the desired amount of hydrogen prior to hydrogen-ation.

This invention relates to analysis of gas streams. In one of its aspects it relates to a method for detecting the presence of hydrogenatable components in a gas stream by passing same over a hydrogenation catalyst and detecting a temperature rise due to hydrogenation of hydrogenatable components within said gas stream.

In another of its aspects the invention relates to an apparatus for detecting the presence of hydrogenatable components in a gas stream, the apparatus comprising a hydrogenation catalyst support means, and means for detecting a temperature rise due to hydrogenation of gas streams passing `across a hydrogenation catalyst on said support means.

Analysis of gas streams is an important part in maintaining proper controls for many chemical processes. It is known to detect oxidizable components by passing the same over an oxidizing means in the presence of oxygen and measuring the rise in temperature due to the oxidation by resistance or thermistor means.

Oleiins may be detected by oxidation but cannot be distinguished from other oxidizable components by oxidation detectors.

I have now discovered that olens can be selectively detected in a stream of non-hydrogenatable hydrocarbons by hydrogenating the oletins in the stream and then sensing the temperature rise due to hydrogenation.

By various aspects of this invention, one or more of the following, or other, objects can be obtained.

It is an object of this invention to provide a method and apparatus for detecting oleins in a stream of saturated hydrocarbons.

A further object of this invention is to provide a method and apparatus for detecting hydrogenatable hydrocarbons in a stream containing the same and non-hydrogenatable hydrocarbons.

It is a still further object of this invention to provide a method and apparatus for selectively detecting and distinguishing between terminally bonded olefins and internally bonded olens in a stream containing the two types of olens.

It is a still further object of this invention to provide a method and apparatus for maintaining xed ratios of hydrocarbons to olens in a gas process stream.

3,488,155 Patented Jan. 6, 1970 Yet another object of this invention is to provide a method and apparatus for detecting the presence of oxygen and other hydrogen reducible materials in a saturated hydrocarbon stream. Other aspects, objects, and several advantages of this lnvention are apparent to one skilled in the art from a study of this disclosure, the drawings, and the appended claims.

According to the invention, hydrogenatable components of a gas stream are analyzed by passing same in the presence of hydrogen over hydrogenation catalyst under hydrogenating conditions and detecting a temperature change due to hydrogenation as a signal representative of the amount of hydrogenatable material in the gas stream.

The hydrogenatable materials can be any materials which exotherrnally or endothermally add hydrogen under hydrogenating conditions. Generally, the materials will be unsaturated hydrocarbons, aldehydes, ketones, alcohols, ethers, organic nitro-compounds (in the presence of amine) and oxygen. The process is especially suitable for detection of olefins in a gas stream of saturated hydrocarbons.

The catalysts which are suitable for the process are any hydrogenation catalysts including Raney nickel, platinum black and palladium black. The preferential catalyst for detecting olens is palladium black.

As has been hereinbefore mentioned, it is necessary that the feedstream to the detector be under hydrogenating conditions. Thus, it may be necessary to heat the feedstream up to a hydrogenation temperature. Suitable hydrogenation temperatures are to 295 C. Unsaturated compounds can be eciently hydrogenated at ISO- C. Alcohols can be hydrogen-ated at 20G-265 C.

In one embodiment of the invention, thermistors are placed upstream and downstream from the hydrogenation catalyst in `a conduit. The temperature differential which is measured by the two thermistors is indicative of the amount of hydrogenatable material in the feedstream. The signals from the thermistors are transmitted to a suitable measuring device which converts the signals into a reading representative of the amount of hydrogenatable materi-al in the stream. This measuring device is therefore a hydrogenation detector.

In another embodiment of the invention, the hydrogenation catalyst is coated directly onto the downstream thermistor and the temperature rise due to the hydrogenation is detected in the same manner as above.

In still another embodiment of the invention, amounts of terminally bonded and internally bonded olens are selectively determined. A mixture of hydrocarbons containing terminally bonded and internally bonded olens are passed to a gas chromatography column and then separated. The separated mixture is passed over the hydrogenation catalyst. The terminally bonded olen will pass over the catalyst `iirst and must be detected first. Thus, the amount of terminally bonded oletin can be determined. Then the internally bonded olefins will pass over the catalyst tand the differential temperature rise for the internally bonded olens will give an indication of the amount of internally bonded olens present.

The various proportions of internally and terminally bonded olens can also be determined without a chromatographic column by simply passing the mixture of gases to a hydrogenation catalyst and detecting the temperature rise due to the hydrogenation of the two types of oleiins. Since the heat of hydrogenation for the two types of olefins is different, the amount of terminally bonded olelins can be determined with respect to the internally bonded olens if the amount of oletins is known. Standard samples with various percentages can be used to make a calibration scale and the temperature rise due to the hydrogenation of the two types of olens can be compared with the standard scales.

The invention will now be described with reference to the drawings in which FIGURE l is a schematic drawing showing an embodiment of the invention as it relates to a gas chromatography column, FIGURE 2 shows a specific detecting device, and FIGURE 3 shows a modified detecting device.

FIGURE 4a is a chart made by a standard thermal conductivity detector (not shown) of the nonhydrogenated mixed olefin and parat-lin etiluent from a chromatographic column, and

FIGURE 4b is a similar chart made by the present hydrogenation detector 9 and 15 of the same nonhydrogenated eiuent from the same chromatographic column 7.

Referring now to FIGURE 1, a gas stream containing hydrogenatable hydrocarbons is passed through line 1. A portion of the gas stream is removed through line 2, passed through sampler valve 3 and a sample thereof is taken through line 5 or returned through line 4 to conduit 1. Hydrogen is used as a purge gas and is also used as a carrier gas and passes with the sample through line 5. Make-up hydrogen can also be added through line 6 as will be hereinafter described. The sample, according to one embodiment of the invention, passes through gas chromatography column 7 which is packed with a suitable material to separate the components of the sample stream. The separated components pass through line 8 to sensor 9 in which the hydrogenatable components-in stream 8 are hydrogenated. The rise in temperature is detected Within detector 9 and a signal representative of the temperature rise is transmitted via lines 13 and 14 to indicator 15 which will give a reading proportional to the amount of hydrogenatable material in gas stream 8. Sensor 9 therefore is a hydrogenation detector having a hydrogenation detector indicator 15. Suitable calibration curves can be made from standard samples and the reading from indicator 15 can be easily converted into a percentage hydrogenatable material in gas stream 8 as is understood by one skilled in the art. The elluent from detector 9 is passed through line 10. The amount of hydrogen in line 10 is detected by hydrogen detector 11 and a signal representative of the hydrogen in stream 10 is sent to recorder controller 12. In the event that the hydrogen content in stream 10 drops below a predetermined limit, a signal will be sent by line 16 to valve 17 to allow more hydrogen to pass through line 6 into line 5. It is desirable in carrying out the process that all of the hydrogenatable material be hydrogenated. Therefore, an excess of hydrogen is required in the process. Alternately and preferably, valve 17 and line 6 can be connected to line 8 to add excess hydrogen between the column and the detector. Addition of hydrogen upstream from the column would change the retention time of the components in the column.

According to another embodiment of the invention, the chromatography column can be by-passed by passing the sample in line 5 through line 18 to line 8. In this case valve 19 will be opened. In the event that it is desirable to use the chromatography column, valve 19 will be closed. The chromatography column will be by-passed in the event that there is only one hydrogenatable material in the sample stream to be detected or when there are two hydrogenatable materials having different heats of hydrogenation as has been hereinbefore described.

If it is desirable to heat the feed to a hydrogenation temperature, this heating is preferably done between column 7 and detector 9. This method will allow the column 7 to be operated at any desired temperature.

Referring now to FIGURE 2, there is shown an embodiment of the invention in which there are two thermistors 20 and 24 to detect the temperature of the gas in line 8. A suitable hydrogenation catalyst such as palladium can be deposited on mesh 22 and placed between the two thermistors. As the gas passes through the stream, hydrogenation of the hydrogenatable materials takes place at 22 and the temperature rise therefrom is detected at 24.

According to another embodiment of the invention, as shown in FIGURE 3, the hydrogenation catalyst is placed directly onto the thermistor, represented by 26. The coating of the catalyst has been greatly exaggerated for purposes of illustration.

Thermistors 20, 24 and- 26 can be any suitable means for measuring the temperature of the gas stream. A suitable thermistor is Veeco AX ll89-2B6 which is normally an 8K resistor at 75 F.

The hydrogen detector 11 can be any suitable hydrogen detector.

The indicator 15 can be any suitable `means for comparing two signals and giving an indication of the relative difference between the signals. A Wheatstone bridge circuit or other suitable means can be employed.

The hydrogenation detecting means 9 and 15 of the invention can be used to maintain a predetermined percentage of olefins in a gas stream. The olens can be detected by the hydrogenation detector 9 and 15 and more or less olens or make-up hydrocarbons can be supplied to the stream in accordance with the measured olen content.

EXAMPLE I A sample containing the components listed in Table A was passed through a 1/8 inch X 16 feet long gas chromatography column containing l0 percent Squalane on 81 mesh Chromosorb G at 40 1C. The effluent from the column was passed to a standard thermal conductivity detector (not shown). The results of the detection in the thermal detector are shown in FIGURE 4a. The numbers correspond to the components listed by the same number in Table A.

TABLE A (3D- normal pentane (32)--3-methy1butene-1 (33)-1,3butadiene (34)-2,2dimethylbutane (3S -2-methy1butene-l (36)-trans pentene-Z (37)-2-methylpentane (38)--3-methylpentane (39)-2-methylbutene-2 (40)-normal hexane (41 -4-methylpentene- 1 (42)-cyclopentene (43)-3,3dimethy1pentane EXAMPLE II A second sample having the same components as Table A was passed through the same gas chromatography column as Example I under the same conditions. The effluent from the column was passed to a hydrogenation detector 9 and 15 according to the invention. The results of this detection are seen in FIGURE 4b.

It can be seen from the above that the invention can be used to advantage todetect the presence of olefms, and for separating pairs of components which are not separated by conventional gas chromatography.

I claim:

1. A method for detecting the presence of a hydrogentable material in a gas stream containing the same and hydrogen, said gas stream being heated to hydrogenation temperature, comprising measuring the temperature of said gas stream, passing said gas stream over a hydrogenation catalyst under hydrogenation conditions, and measuring the temperature of said gas stream after hydrogenation, whereby the change in temperature indicates hydrogenatable materials.

2. A method according to claim 1 wherein olens are detected in said gas stream.

3. A method according to claim 1 where said gas stream is rst passed through a gas chromatography column to separate the various components and hydrogenatable materials are serially detected by sensing the resulting change in temperature of said gas stream for each material as it is hydrogenated in serial order.

4. A method according to claim 1 wherein said hydrogenation catalyst is selected from the group consisting of Raney nickel, platinum black and palladium black.

5. A method according to claim 4 wherein said catalyst is palladium.

6. A method according to claim 1 wherein said hydrogenation material is oxygen.

7. A method according to claim 1 wherein the ratio of hydrocarbons to olens is maintained in said gas stream lby further using the signal detected from said temperature change as an indication of the amount of olens in said hydrocarbon stream, comparing said amount with a predetermined amount, and adjusting the percentage of olefins in said stream according to said comparison by changing the amount of at least one of the hydrocarbons and the olens of said stream in an amount suicient to maintain said predetermined hydrocarbons to olens ratio.

8. A method according to claim 1 wherein the hydrogen remaining in the gas after hydrogenation is measured and used to control the rate of addition of hydrogen to said stream before hydrogenation so that said hydrogenation will be substantially complete.

9. An apparatus for detecting the presence of hydrogenatable material in a gas stream containing the same and hydrogen comprising conduit means heated to hydrogenation temperature, in said conduit means a hydrogenation catalyst support means having a hydrogenation catalyst thereon, and a means for detecting a temperature change in said conduit means due to hydrogenation of said hydrogenatable material.

10. An apparatus according to claim 9 wherein there is further provided a gas chromatography column upstream from said conduit means and in open communication with said conduit means.

11. An apparatus according to claim 9 wherein said detecting means comprises a rst thermistor and a second` thermistor, said second thermistor being downstream from said first thermistor, said first and second thermistors being operably connected to a comparing and indicating means `which means gives an indication of the difference between the signal generated from said rst and said second thermistor means, and wherein said hydrogenation catalyst support means is between said first and said second thermistor means.

12. An apparatus according to claim 9 wherein said detecting means comprises two thermal detector means, one downstream from the other, wherein said detecting means comprises a rst and a second thermal detection means, said second thermal detection means being downstream from said rst thermal detection means, said second detection means having thereon said hydrogenation catalyst support means, and said rst and said second thermal detector means being operably connected to a comparing and sensing means which gives a visual indication of the difference between the signal generated from said tirst and said second thermal detecting means.

13. The apparatus according to claim 9 wherein there is further provided a hydrogen detector in the outlet from said conduit means, and means controlled by said hydrogen detector to vary the rate at which hydrogen is added to the inlet of said conduit means so that said hydrogenation will be substantially complete.

References Cited UNITED STATES PATENTS 2,762,568 9/1956 Sullivan.

2,901,329 8/1959 Kapf.

2,905,536 9/1959 Emmett et al 23-232 3,030,191 4/1962 Ridgway et al. 23-232 FOREIGN PATENTS 832,423 4/1960 Great Britain.

MORRIS O. WOLK, Primary Examiner R. M. REESIE, Assistant Examiner U.S. Cl. X.R.

PRIN l ln n lruM UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,488,155 Dated Januajr 6. 1970 Inventor(s) Buell O. Ayers It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5 Claim 6 lines 12 ,13 "hydrogenation" should be corrected to read hydrogenatable Column 6 Claim l2 lines 13 14 between the words "second" and "detection" should be inserted thermal SIG NED AND SEALED JuL141970 )I Auen:

EdwardllFletchex-,In

mung officer 

